Firing circuit



M. APSTEIN FIRING CIRCUIT June 16, 1959 2,890,655

Fiied March '7, 195a 'FIRING '8 SIGNAL |DETONATOR Li M INVENTOR Maurice Apsfein I ATTORNEY}.

United States Paten FG CIRCUIT Maurice Apstein, Bethesda, Md., assignor to the United States of America as represented by the Secretary of the Army Application March 7, 1956, Serial No. 570,189

2 Claims. (Cl. 102-70.2)

(Granted under title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without payment to me of any royalty thereon.

This invention relates to ordnance fuzes and more particularly to firing a detonator by a thyratron.

In many fuzes the detonator is fired in response to a signal relayed by electronic circuits. As this signal is weak, one type firing circuit of a device of this nature is a thyratron that receives the firing signal at its grid and then triggers, releasing a charge stored in a capacitor through the detonator. As these devices must be small in size and light in weight, it is desirable to use a detonator requiring small energy to fire it, such as a carbon bridge detonator. When a low energy detonator is used, a smaller capacitor, thyratron, and power supply may also be used. However, this capacitor is not charged until the vehicle carrying the device is launched; therefore this capacitor must be charged fairly quickly. The capacitor is charged through the detonator itself and if a sensitive detonator is used there is danger that the detonator will be fired by the capacitor charging current.

This invention solves this problem by shunting the deto'nator with a small inductor that will readily pass the charging current but will block the sharp pulse of firing current, sending it through the detonator.

An object of this invention is to provide a small and safe firing circuit for a proximity fuze.

A further object is to achieve the above with a device that is sturdy, simple, and reliable, yet cheap and easy to manufacture.

The specific nature of the invention as well as other objects, uses and advantages thereof will clearly appear from the following description and from the accompanying drawing in which:

The drawing is a schematic representation of the firing circuit of a fuze according to this invention.

In the drawing, switch 1 is adapted to close automatically by means not shown when a containing vehicie (also not shown) is launched. When switch 1 closes it applies B+ charging current from source 2 to capacitor 3 through resistor 4 and inductor 5 that shunts detonator 6. The rate of charging of capacitor 3 is controlled principally by the value of resistor 4. Inductor 5 has relatively low direct current resistance but relatively high inductance in relation to detonator 6. Because the charging current pulse has a relatively slow rise rate it passes through inductance 5; detonator 6 is thus protected against detonation at this time. When a firing signal applied to grid 7 triggers thyratron 8, however, a dis charge current pulse having a relatively fast rise rate flows through the parallel detonator 6inductor 5 combination. Inductor 5 presents a relatively high impedance to this fast pulse; practically all of the pulse passes through detonator 6, and detonator 6 fires.

It will be apparent that the embodiment shown is only exemplary and that various modifications can be made in construction, materials, and arrangement within the scope of the invention as defined in the appended claims.

I claim:

1. An ordnance fuze firing circuit comprising in combination: a detonator which fires when a small amount of electrical energy is applied to it, said detonator having one end connected to circuit ground; an inductor connected in shunt with said detonator, said inductor having a relatively high inductance in relation to said detonator so that a slowly changing current will pass largely through said inductor While a rapidly changing current will pass largely through said detonator; a thyratron having plate, grid and cathode elements, said cathode being connected to circuit ground and said grid being connected to receive a firing pulse; a capacitor having one end connected to the ungrounded end of said detonator and the other end connected to said thyratron plate; a source of direct current voltage having positive and negative ends, the negative end being connected to circuit ground; and a resistor and a normally open switch connected in series between the positive end of said source and said thyratron plate, said switch being adapted to automatically close at a predetermined time after launching, and said resistor having a value such that said capacitor charges at a relatively slow rate when said switch is closed; said source charging said capacitor to a voltage which causes breakdown between the plate and cathode of said thyratron when said grid receives a firing pulse, a rapidly changing discharge current thereupon passing through said detonator causing said detonator to fire.

2. In an ordnance tuze firing circuit comprising a positive voltage source, a resistor having one end connected to said source, a thyratron having a plate, cathode and grid, the plate of said thyratron being connected to the other end of said resistor and the cathode being connected to circuit ground, a capacitor having one end connected to said plate, and a detonator having one end connected to circuit ground and the other end connected to the other end of said capacitor, the improvement comprising: an inductor shunting said detonator so that a slowly changing current will pass largely through said inductor while a rapidly changing current will pass largely through said detonator.

References Cited in the file of this patent UNITED STATES PATENTS 1,133,183 Reineke Mar. 23, 1915 2,404,553 Wales July 23, 1946 2,672,813 Conner Mar. 23, 1954 

